Installations comprising several free piston autogenerators supplying a receiver with driving gases



Nov. 12, 1968 P. P. SZERESZEWSKI 3,410,307

INSTALLATIONS COMPRISING SEVERAL FREE PISTON AUTOGENERATORS SUPPLYING ARECEIVER WITH DRIVING GASES Filed June 9, 1965 3 Sheets-Sheet l lNVE/VTOR P/MCHAS 'PAu/ \sze-rzeszsws i z, and W ATTORNEYS N 1968 P. P.SZERESZEWSKI 3,410,307

INSTALLATIONS COMPRISING SEVERAL FREE PISTON AUTOGENERATORS SUPPLYING ARECEIVER WITH DRIVING GASES Filed June 9, 1965 3 Sheets-Sheet 2 \at f a/NVE/\/TUR TD/IVQHAS 7 00/ Szsrees 2.5a) sm' ATTORNEYS Nov. 12, 19683,410,307

INSTALLATIONS COMPRISING SEVERAL FREE PISTON AUTOGENERATORS P. P.SZERESZEWSKI SUPPLYING A RECEIVER WITH DRIVING GASES 3 Sheets-Sheet 5Filed June 9, 1965 ATTORNEYS United States Patent 3,410,307INSTALLATIONS COMPRISING SEVERAL FREE PISTON AUTOGENERATORS SUPPLYING ARECEIVER WITH DRIVING GASES Pinchas Paul Szereszewski, Asnieres, France,assignor to Societe dEtudes et de Participations Eau, Gaz, Electricite,Energie, S.A., Geneva, Switzerland Filed June 9, 1965, Ser. No. 462,664Claims priority, application France, June 10, 1964, 977,819 7 Claims.(Cl. 137--610) ABSTRACT OF THE DISCLOSURE The invention relates to meansfor automatically controlling the motion speeds of the valve members ofthree way valve systems between positions where they respectivelyconnect the free piston autogenerators of an installation constituted ofseveral of said autogenerators with either a receiver engine, such as aturbine, which is to be supplied with the driving gases produced by saidautogenerators or the atmosphere, said autogenerators being connectedwith both for intermediate positions of said valve members. These meansare adapted to restrain the speed of the motion of each of said valvemembers when it is desired to connect the corresponding autogeneratorwith the receiver engine as well as, preferably, on the last portion ofthe travel of said valve member in the opposite direction.

The invention relates to installations comprising several free pistonautogenerators which supply a receiver, in particular a turbine, withdriving gases.

It is known to connect the exhaust outlets for driving gases generatedby several autogenerators of a common installation to a common collectorlocated upstream from the receiver engine and to provide between eachautogenerator respectively and the common collector a three way valvesystem comprising a valve which, dependant upon its positions in saidsystem, controls either the connection between the correspondingautogenerator and the collector, or the connection between saidautogenerator and a space under low pressure such as the atmosphere, .orfurther the connection between said autogenerator and both the collectorand the atmosphere.

The control of the known three way valve systems requires from thesupervisor of the installation a great attention and the performance ofa certain number of successive operations in the case, for instance,where one of the autogenerators is to be started and connected to thecommon collector at a time where the other autogenerators of the sameinstallation are already working.

The object of the invention is to simplify the operations to beperformed by said supervisor and to automatize the motions of the valveas soon as they are started in one direction or in the other either bythe supervisor or by a governor.

The invention is more particularly concerned with the control of a threeway valve system provided, between each autogenerator and the collector,upstream from the receiver and which is likely, in its extremepositions, to connect the autogenerator either with the receiver or witha space under low pressure for instance the atmosphere, whereas, in itsintermediate positions, it permits more or less throttled connectionsbetween the autogenerator and, on the one hand, the collector and, onthe other hand, the space under low pressure.

According to the invention, the control means for the operation of thevalve member of said three way valve system are arranged in such mannerthat they automatiice cally cause, when it is desired to connect theautogenerator with the collector, a slow motion of the valve with aprogressive increase of the section of the throttled communicationbetween the autogenerator and the collector and a concomitantprogressive decrease of the section of the throttled communicationbetween the autogenerator and said space under low pressure whereas,when it is desired to disconnect the autogenerator from the collector,they cause a rapid motion of said valve member, at least in the firstportion of the stroke thereof, toward the position in which said valvemember closes the communication between the autognerator and thecollector and opens completely the communication between theautogenerator and the space under low pressure.

According to a preferred embodiment of the invention, said valve iscontrived in a manner such that it comprises, on either side of the partof its body which carries the surfaces coming into contact with valveseats provided in the chamber of said three way valve system for closingcompletely the communication between the autogenerator and either thecollector in one of its extreme positions or the space under lowpressure in its other extreme position, protruding extensions therespective diameters of which decrease toward their extremities so thatthey cooperate with the one or the other of said valve seats forproducing said throttled connections between the autogenerator and, onthe one hand, the collector and, on the other hand, the space under lowpressure, the sections of said throttled connection varyingprogressively when said valve member moves progressively from one ofsaid seats to the other.

Other objects of the invention will appear as this description proceedsin connection with preferred but nonlimitative embodiments of saidinvention and with reference to the appended drawings in which:

FIG. 1 shows diagrammatically a part of the installation in accordancewith the invention, said part comprising in particular one of theautogenerators supplying the collector of the installation with drivinggases and means controlling the communication of this autogeneratoreither with the collector or with the atmosphere:

FIGS. 2, 3 and 4 show the said control means in several operatingpositions;

FIG. 5 is a diagram showing the respective evolutions of the deliverypressure when one of the autogenerators is connected with the commoncollector for two different working conditions of said installation.

FIGS. 6 to 8 show other exemplary embodiments, according to theinvention, of the means controlling the operation of said three wayvalve system.

Referring first to FIGURES 1 to 4, they show an installation comprisingfor instance three piston autogenerators and a turbine fed with drivinggases supplied by said autogenerators.

The installation comprises a collector 1 and three gas supply pipes 2 22 leading thereto, each of said pip s connecting one autogenerator tosaid collector. Only one of said autogenerators shown at 3 isrepresented in FIG. 1, this autogenerator being connected to the pipe2,. The collector 1 is further connected through a pipe 4 to a turbine 5which is driven :by the driving gases supplied by the workingautogenerators to the collector 1.

Each of said free piston autogenerators comprises, as well known, adriving or motor part working preferably according to a two strokediesel cycle and a compressor part compressing and delivering air to themotor part. The driving gases delivered by the autogenerator areconstituted by the mixture of uncompletely expanded combustion gasesformed therein and of the excess of scavenging air supplied by thecompressor part to the motor part. After its exhaust from said motorpart, this mixture arrives first to an exhaust pot 6 and afterwards to athree way valve system 7 within which a valve member 8 is provided. Thisthree way valve system is connected, on the one hand, to said exhaustpot 6, on the other hand to the pipe 2,, communicating with thecollector 1 and finally to a conduit 9 which opens to the atmosphere. Inthe position shown in FIG. 1, the valve member 8 closes thecommunication between the exhaust pot 6 and the pipe 2,, by itsapplication on the valve seat 8 and it permits the large opening of thecommunication between said exhaust pot and the conduit 9.

In the positions shown in FIGS. 2 and 4, said valve member providesthrottled communications between the exhaust pot 6 and simultaneouslythe collector 1 on the one hand, and the conduit 9 on the other hand.

Finally, in the position shown in FIG. 3, the valve member opens fullythe communication between the exhaust pot 6 and the collector 1 andcloses the communication between the exhaust pot 6 and the conduit 9 byits application against the valve seat 8 Concerning the control means ofsaid valve member, for opening for example the connection between oneautogenerator 3 and the collector 1 supplied under a given pressure withthe driving gases from other autogenerators of the same installation,they are arranged, according to the invention, in a manner such thatthey cause a slow motion of the valve member in the direction of theopening of the communication between the newly started autogenerator 3and the pipe 2 which leads to the collector 1 and the concomitantclosing of the communication between the same autogenerator 3 and theconduit 9, so that the pressure of the gases supplied by theautogenerator 3 may increase progressively and that consequently anequalization occurs between the pressures existing in the exhaust pot 6and the collector 1.

During the slow motion permitting the connection of the autogenerator 3with the collector 1, the valve 8, starting from the position shown inFIG. 1, passes through the intermediate position such as shown in FIG. 2and finally stops at the end of the connection period in the positionshown in FIG. 3 in which it opens a large communication between theexhaust pot 6 and the collector and closes completely the conduit 9.

FIG. 5 shows the changes in the pressures within the exhaust pot 6during the performance of this connection operation in the case, on theone hand, where the pressure in the collector 1 is relatively high, forinstance equals 3 atmospheres and, on the other hand, where the pressurein the same collector is low, for instance equals or nears 0 atmosphere.The abscissae in said diagram correspond to the stroke of the valvemember 8 or to the time of duration of said stroke, whereas theordinates correspond to the pressures in the exhaust pot 6.

In the two cases it can be seen that the pressure within the exhaust pot6 first increases up to an intermediate position of the valve member. Inthe first case, the pressure further increases beyond this intermediateposition to approximately equal said pressure of 3 atmospheres withinthe collector. However, in the second case, the pressure within theexhaust pot 6 decreases after this intermediate position of the valvemember to become approximately equal to the one existing in thecollector 1, thus practically to the atmospheric pressure.

Still according to the invention the control means of the valve member 8are arranged such that they control a rapid return stroke of said valvemember-namely in the direction where it opens the communication betweenthe exhaust pot 6 of the autogenerator 3 and the conduit 9 and closes atleast partially the communication between said exhaust pot 6 and thecollector 1at least in the first part of said stroke. This last motionof the valve member permits the decrease and the suppression of thefeeding of the turbine by the concerned autogenerator when the load ofthe same suddenly decreases, for

instance on the case of the cut out of an alternator driven by saidturbine.

According to a preferred embodiment of the invention, one provides thatthis rapid motion which produces a rapid decrease of the delivery ofdriving gases from the concerned autogenerator to the collector isstopped before the complete closing of the pipe 2 by said valve member,in an intermediate position, for instance in the one shown in FIG. 4,the further motion of said valve in the same direction being againslowed down. In such a manner, the supply of gases to the collector 1 issufliciently reduced and one avoids a too rapid decrease of the pressurewithin the exhaust pot 6, such a too rapid decrease in pressure beinglikely to stop the autogenerator 3. Another reason which justifies theslow operation of the end portion of the return-stroke of the valvemember 8 in the direction of closure of the pipe 2,, lies in the factthat the sudden decrease in load of the turbine lasts only a short time,for instance during only a few seconds, and that afterwards the valvemember 8 must permit the passage of sufficient quantities of gas towardthe turbine in order to maintain the turbine in idling operation or, ifthe case should be, to enable the same to deliver a reduced power.

The valve member 8 is advantageously provided, on either side of itsmedian portion which carries the surfaces resting against the valveseats 8 or 8 for the extreme positions of the valve member, withprotruding extensions 10 and 11 the diameters of which decrease towardtheir extremities and the side surfaces of which cooperate with theseats 8,, and 8,, respectively, for con trolling the increase ordecrease of the sections of the throttled passage for the gases betweenthe exhaust pot 6 and the pipe 2,, as well as between the exhaust pot 6and the conduit 9, according to predetermined laws, during the motionsin either direction of said valve member. The generating lines of theside walls of said protruding extensions are chosen such as tocorrespond to the desired laws of variation of the sections of saidthrottled passages in function of the intermediate positions of saidvalve member.

The control means of the valve 8 such as defined here above may be ofdifferent nature, for instance of pneumatic, hydraulic or electricnature.

A preferred hydraulic embodiment of the control means according to theinvention which appears to be particularly advantageous is shown inFIGS. 1 to 4.

According to this embodiment, the valve member 8 is mounted on a rod 12carrying a piston 13 which divides one cylinder 14 in two compartments aand b. The cylinder 14, which is closed on the side directed toward thevalve 8, is provided with an inlet 15 for a liquid under pressure andopens by its other side into a second cylinder 16 having a largerdiameter. A piston 17, which is slidably fitted on an extension 12 ofthe rod 12, works in said cylinder 16 (FIG. 1), the extension 12,,extending beyond the piston 13 on the opposite side thereof with respectto the valve member 8. The compartment b is thus limited on one side bythe piston 13 and on the other side by the piston 17. The compartment 0of cylinder 16 which is located on the opposite side of the piston 17communicates with an accumulator 20 of fluid under pressure through anopening 18 controlled by a valve 19.

The compartments b and c are interconnected by a conduit 21 providedwith a throttle 22. In addition, another conduit 23, equally comprisinga throttle 24, is connected with the conduit 21.

The valve 19, as shown in FIGS. 1 to 4, is shaped as a stepped piston,the part thereof having the smaller diameter closing the opening 18 whensaid part is applied against the border of said opening. Said part ofsmaller diameter works in a space d having a larger diameter which isconnected with the accumulator 20 through a conduit 25.

The portion of the valve 19 having the largest diameter operates in acylinder 26, a spring 27 being lodged therein, said spring tending tomove the valve 19 toward the opening 18 in order to ensure the closingthereof. In addition, the bottom of said cylinder 26 is connectedthrough a conduit 28 and an electrovalve 29, either with the accumulator20 through a further conduit 31 or with the atmosphere through an outlet31. The pressure generated in the accumulator 20 is far superior to thepressure which is fed by the inlet into the compartment (1. For instancethe pressure in compartment a is equal to 3 atmospheres whereas thepressure which is permanently generated in the accumulator is forinstance equal to 12 atmospheres. This pressure is maintained in theaccumulator 20 by a pump not represented.

The operation of the control means which have been described here aboveis as follows.

In is assumed first that the valve member 8 is in the position shown inFIG. 1, that is to say in the position for which it closes thecommunication between the exhaust pot 6 of the autogenerator 3 and thecollector 1 and enables the communication of said exhaust pot with theconduit 9.

In order to maintain the valve member 8 in this position, theelectrovalve 29 is in the position shown equally in FIG. 1. In such aposition, it closes the communication between the accumulator 20 and theinterior space of the valve 19 within the cylinder 26. Consequently, thepressure which reigns in the accumulator 20, and which is supplied inthe space a by its action upon the shoulder 19 formed by the portionhaving the largest diameter of the valve 19, maintains the same againstthe spring 27 in the position for which the opening 18 is open.

Thus the pressure in the accumulator 20 is transferred to the space cwithin which it acts on piston 17 to apply the same against an abutmentshoulder 32. In addition, the pressure of the accumulator is fed throughthe conduit 21 and the throttle 22 in the compartment b of the cylinder14 and thus acts on the piston 13 which maintains the valve member 8 inthe position shown in FIG. 1 since the pressure fed by the accumulator20 is higher than the pressure fed to the compartment a through theinlet .15. When it is desired to connect the autogenerator 3, after itsstarting, with the collector 1, the electrovalve 29 is brought into theposition shown in FIG. 2. In this position, it opens the communicationof the accumulator 20 with the cylinder 26. The pressure of saidaccumulator, reinforced by the action of the spring 27, causes the valve19 to move to the position for which its closes the opening 18 (see FIG.2). Hence the spaces 0 and b are cut off from the accumulator 20. Thepressure still existing in the compartment a thus causes the motionfirst of the piston 13 slowly toward the right side against theresistance of the liquid contained in the compartment b and whichescapes through conduits 21 and 23 and the throttles 22 and 24. Afterthe piston 13 has moved along a first part of its range of motion in theright direction with respect to the valve member 8, it abuts anextension 17, of the piston 17 so that the latter starts, under thedriving effect of the pressure in the compartment 0, to move also to theright, this last motion being also slowed down owing to the fact thatthe piston 17 must drive out the liquid contained in the compartment 0through the conduit 23 and throttle 24. The motion of the valve member 8and of the pistons 13 and 17 to the right is stopped when the medianpart of said valve member comes into contact with the valve seat 8 thatis to say in the position where said valve member opens thecommunication between the exhaust pot 6 of the autogener-ator 3 and thecollector 1 and concomitantly closes the communication between saidexhaust pot 6 and conduit 9. The slow motion of the valve memher fromleft to right has been obtained through the resistance opposed by theliquid in the compartments b and c to the action of the pistons 13 and17. Thus the pressure in the exhaust pot 6 has had the time to adaptitself to the pressure in the collector 1.

In the positions shown in FIG. 3, the valve member 8 and its controlelements connect completely the autogenerator 3 with the collector 1. Ifit is desired to dis connect the autogenerator 3 from the collector 1,the electrovalve 29 is again brought into the position shown in FIG. 1and equally in FIG. 4. As a consequence, the valve 19 opens, followingthe setting in communication of the cylinder 26 With the atmospherewhereas the shoulder 19,, of the valve 19 is still subjected to thepressure of the accumulator 20. The consequence of the opening of thevalve 19 is the immediate action of the pressure reigning in theaccumulator 20 on the piston 17. Owing to the importance of thispressure, both pistons 17 and 13, together with the: valve member 8, aremoved rapidly to the left from the position shown in FIG. 3 to theintermediate position shown in FIG. 4 in which the piston 17 is stoppedby its application against the abutment shoulder 32. For thisintermediate position of the valve member 8, the flow of the drivinggases generated in the autogenerator 3 toward the collector 1 isstrongly reduced. If the electrovalve 29 remains in the last position,the valve 8 is caused to proceed further to the left under the action ofthe pressure in the accumulator 20 which is supplied to the piston 13through the throttle 22 against the pressure existing in the compartmenta. Thus the further motion of the valve member 8 toward the left,starting from the intermediate position shown in FIG. 4, is stronglyslowed down.

It can be noted that a flap 33 has been shown in the conduit 9 in FIGS.1 to 4. This flap is only used to cause the variation of pressure in theexhaust pot 6 in the case where the autogenerator 3, which has beenstarted, is not immediately connected with the collector 1. Consequentlythe flap 33 is of no use in the normal situation where it is desired toconnect the autogenerator 3, after its starting, with the collector. Inthis last instance, all the operations are performed by the motions ofthe valve member 8.

Of course many alternatives of the control means of the valve member 8in the chamber of said three Way valve system 7 can be contrived withoutdeparting from the scope of the invention. Such alternatives arerepresented in FIGURES 6 to 8.

In FIG. 6 the embodiment represented in FIGS. 1 to 4 is slightlymodified to have the same pressure accumulator delivering fluid underpressure either to the compartment c of cylinder 16 or in thecompartment a of cylinder 14. This may be achieved for instance byconnecting conduit 23 to inlet 15 by a line 35 and by further connectingthe electrovalve 29 to said line 35 through a line 36 (FIGURE 6).

It will be appreciated that when the electrovalve 29 is in the positionshown in FIG. 6 it enables the accumulator to supply fluid underpressure in the compartment c of cylinder 16 while the compartment a isopen to the atmosphere, thereby ensuring the closure of the connectionbetween the collector 1 and the exhaust means 6 in the aforesaidconditions.

On the contrary when the electrovalve is in the position shown inFIGURES 2 and 3 it enables the supply of the compartment (1 of cylinder14 with fluid under pressure while it operates valve 19 to close theopening 18 of the compartment c of cylinder 16. The fluid pressureacting on piston 13 thus move the same slowly in the direction wheresaid valve member opens the connection between said exhaust means 6 andsaid collector 1 against the resistance of the fluid compartment b and0.

Still another embodiment is shown in FIGURES 7 and 8 in which the sameelements than in the former figures are referred to by the samereference numbers. An accumulator 40 of fluid under pressure iscontrolled by an electrovalve 41 to supply said fluid under pressureeither through a line 42, to the exterior compartment a defined by thepiston 13 in the cylinder 43 of the control means for the displacementsof said valve member 8 or, through a line 44, to the exteriorcompartment 0 defined in said cylinder 42 by the piston 17.

FIG. 7 shows the electrovalve 41 in the position in which it allows thefluid under pressure to be fed in said compartment c while compartment ais connected with the atmosphere through line 42 and outlet 45. Asdescribed above piston 17 is then able to push rapidly piston 13together with the valve member 8 in the direction where the lattercloses partially the connection between said collector and said exhaustmeans until said piston 17 is stopped by abutment 46. The piston 13 isthen allowed to move further but slowly in the same direction untilcomplete closure of the last lmcntioned connection owing to the supplyunder reduced flow of fluid under pressure in the central compartment bthrough line 21 throttled in 22.

On the contrary when electrovalve 41 is in the position shown in FIG. 8it is the compartment a which is connected with the source of fluidunder pressure 'while the supply to compartment 0 is cut off. Thepressure in cornpartment a is thus able to move piston 13 toward piston17, the former driving the latter away from its abutment 46 in the lastportion of its stroke, the motions of said pistons in the last mentioneddirection being slowed down owing to the reduced flow of the fluiddriven out from compartments b and c In a general manner, while theabove description discloses what are deemed to be practical andeflicient embodi ments of the present invention, said invention is notlimited thereto as there might be changes made in the arrangement,disposition and form of the parts without departing from the principleof the invention as comprehended within the scope of the appendedclaims.

What is claimed is:

1. An installation comprising free piston autogenerators, each of whichis provided with exhaust means, a collector, communication means betweeneach of said exhaust means and said collector, a three way valve systemwithin said communication means, said three way valve system comprisinga chamber connected to the concerned exhaust means, the collector and aspace under low pressure, a valve member in said chamber which in afirst extreme position connects said exhaust means to said collectoronly, in a second extreme position connects said exhaust means to saidspace only, and, in intermediate positions between said extremepositions, provides throttled communications of said exhaust means withboth said collector and said space, said valve member being shaped suchthat the sections of the respective throttled communications varyregularly in function of the respective distances between anyintermediate position considered and the extreme positions respectivelyof said valve member, means operative to move said valve member ineither direction between said first and second respective extremepositions and means for restraining the speed of the motion of saidvalve from said second extreme position, where it connects said exhaustmeans to said space only, toward said first extreme position where itconnects said exhaust means to said collector only.

2. An installation according to claim 1 further comprising means forrestraining the speed of the motion of said valve from an intermediateposition thereof toward said second extreme position where it connectssaid exhaust means to said space only.

3. An installation according to claim 1 wherein the communicationsbetween said chamber and respectively said collector and said spaceunder low pressure are provided with seats for said valve member, thelatter comprising two protruding portions extending from either side ofthe surfaces of said valve member coming respectively in contact withsaid seats in either one of said first and second extreme positions,said protruding portions cooperating with said seats for ensuring saidregular variations of the sections of said throttled communications infunction of the respective distances of said intermediate positions ofsaid valve member to said extreme positions.

4. An installation comprising free piston autogenerators, each of whichis provided with exhaust means, a collector, communication means betweeneach of said exhaust means and said collectors, a three way valve systemwithin said communication means, said three Way valve system comprisinga chamber connected to the concerned exhaust means, the collector and aspace under low pressure, a valve member in said chamber which in afirst extreme position connects said exhaust means to said collectoronly, in a second extreme position connects said exhaust means to saidspace only, and, in intermediate positions between said extremepositions, provides throttled communications of said exhaust means withboth said collector and said space, a system comprising a cylinder and apiston working in said cylinder, said piston being rigid with said valvemember for controlling the displacements thereof, sources for supplyingin said cylinder fluid under different pressures in said cylinder on theopposite sides of said piston, the higher pressure being fed on the sideof said piston where it causes the same to move said valve member in thedirection where it closes the connection between said collector and saidexhaust means, a throttled outlet in said cylinder on the side of thepiston subjected to the highest fluid pressure, means operative to cutoff the connection between the source supplying the highest pressure andsaid cylinder, thereby enabling the lower pressure fluid to move thepiston in the direction where it opens the connection between saidexhaust means and said collector, said piston being slowed down duringthis motion by the limited flow of the fluid driven out from saidcylinder through said throttled outlet.

5. An installation comprising free piston autogenerators, each of whichis provided with exhaust means, a collector, communication means betweeneach of said exhaust means and said collectors, a three way valve systemwithin said communication means, said three way valve system comprisinga chamber connected to the concerned exhaust means, the collector and aspace under low pressure, a valve member in said chamber which in afirst extreme position connects said exhaust means to said collectoronly, in a second extreme position connects said exhaust means to saidspace only, and, in intermediate positions between said extremepositions, provides throttled communications of said exhaust means withboth said collector and said space, a system comprising cylinder means,a first piston rigidly connected to said valve member and a secondpiston slidable in said cylinder means, an abutment in the centralcompartment defined in said cylinder between said first and secondpistons for limiting the displacements of said second piston toward saidfirst piston, means for supplying fluid under a lower pressure and ahigher pressure to respectively the first and second exteriorcompartments defined in said cylinder by said first and second pistons,control means operative to cut off the highest pressure supplied to saidsecond compartment, a throttled connection between said centralcompartment and said second compartment, a throttled outlet from saidsecond compartment, said first piston being so positioned in saidcylinder means with respect to said second piston that, when saidcontrol means are operated to cut off the highest pressure supply offluid to said second compartment, said first piston moves said valvemember in the direction where it opens the connection between saidcollector and said exhaust means and, during its stroke, abuts saidsecond piston and drives it away from said abutment, said first pistonbeing slowed down during said stroke by the limited flow of the fluiddriven out through said throttled outlet whereas, when said controlmeans are operated to permit the supply of the highest pressure on saidsecond piston it is rapidly pushed back until said abutment togetherwith said first piston, the latter being then caused to end slowly thesecond portion of its return stroke under the fluid supplied to itthrough said throttled connection.

6. An installation according to claim wherein the diameter of saidsecond piston is greater than the diameter of said first piston.

7. An installation comprising free piston autogenerators, each of whichis provided with exhaust means, a collector, communication means betweeneach of said exhaust means and said collectors, a three way valve systemwithin said communication means, said three way valve system comprisinga chamber connected to the concerned exhaust means, the collector and aspace under low pres sure, a valve member in said chamber which in afirst extreme position connects said exhaust means to said collectoronly, in a second extreme position connects said exhaust means to saidspace only, and, in intermediate positions between said extremepositions, provides throttled communications of said exhaust means withboth said collector and said space, a system comprising a cylinder, afirst piston rigidly connected to said valve member and a second pistonslidably fit in said cylinder, an abutment in the central compartmentdefined in said cylinder between said first and second pistons forlimiting the displacements of said second piston toward said firstpiston, means for supplying a fluid under pressure, control means insaid last mentioned means operable to permit the supply of either one ofthe first and second exterior compartments defined in said cylinder bysaid first and second pistons respectively, a throttled connectionbetween said second compartment and said central compartment, athrottled outlet from said second compartment, said first piston beingso positioned in said cylinder with respect to said second piston that,when said control means are operated to supply said fluid under pressureto said first compartment, said first piston moves said valve member inthe direction where it opens the connection between said collector andsaid exhaust means and, during its stroke, abuts said second piston anddrives it away from said abutment, said first piston being slowed downduring said stroke by the limited flow of the fluid driven out from saidsecond compartment through said throttled outlet whereas, when saidcontrol means are operated to permit the supply of said secondcompartment with fluid under pressure, said second piston is rapidlypushed back until said abutment together with said first piston, thelatter being then caused to end slowly the second portion of its returnstroke under the fluid supplied to it through said throttled connection.

References Cited UNITED STATES PATENTS 1,718,673 6/1929 Wettstein 25126X 2,148,616 2/1939 Gruber 91-189 X 2,206,957 7/1940 Hose 25126 2,327,9428/1943 Thoresen 137609 X 2,517,061 8/1950 Stackelberg 137-625. 112,981,290 4/1961 Meyer 251-122 X 2,991,631 7/1961 Ray 137-62511 X3,199,536 8/1965 Thompson 137609 FOREIGN PATENTS 451,779 10/1948 Canada.

WILLIAM F. ODEA, Primary Examiner. D. H. LAMBERT, Assistant Examiner.

